Fluid blast interrupting device for oil circuit breakers



Dec. 4, 1962 J- M. RAMRATH 3,067,307

FLUID BLAST INTERRUPTING DEVICE FOR OIL CIRCUIT BREAKERS 5 Sheets-Sheet1 Filed Jan. 15, 1960 300% W. gamma/W Dec. 4, 1962 J. M. RAMRATH FLUIDBLAST INTERRUPTING DEVICE FOR OIL CIRCUIT BREAKERS 3 Sheets-Sheet 2Filed Jan. 15, 1960 @ubkwww Dec. 4, 1962 J. M, RAMRATH 3,067,307

FLUID BLAST INTERRUPTING DEVICE FOR OIL CIRCUIT BREAKERS Filed Jan. 15,1960 5 Sheets-Sheet 3 trite This invention relates to electric circuitinterrupters and more particularly to high speed oil circuit breakers ofthe fluid blast type.

More specifically this invention relates to a novel structure foreffecting the very rapid initiation, elongation and extinction ofelectric arcs drawn in circuit interrupters. This invention isapplicable to the interruption of high voltage arcs such as those drawnin 287 kv. circuits but is also applicable on low voltage circuits.

It is known that a rapid lowering of the dielectric strength of an arcextinguishing fluid, such as oil, occurs after it impinges upon the arcstream and that it is desirable to eliminate such contaminated fluid asquickly as possible and to subject the arc stream to the action of freshfluid of high dielectric strength. The isolation or disconnection of acapacitance load by a circuit breaker in an alternating current systemis subject to transient overvoltages, the magnitudes of which depend onthe capacitance of the load, the voltage of the system and the type ofthe circuit breaker. In one-half cycle after the first current zero, thevoltage of the source has reversed to its crest value and approximatelydouble this voltage appears across the circuit breaker contacts as acircuit recovery voltage. Whether or not restriking of the arc occursdepends on several factors such as the type of the circuit breakerincluding the speed and the magnitude of the separation of its contacts,the magnitude of the circuit recovery voltage, and the leading kva. ofthe load.

In the oil blast circuit breakers of the prior art interrupting devicesequipped with oil pistons for efficient interruption of magnetizing andcapacitive currents generally use separate push rods for theiroperation. This arrangement positions the centers of the contact rod andpush rod in different planes resulting in expensive and space consuminginterrupting devices, complicated bridging contacts and large oil tanks.

In accordance with the invention claimed a new and improved coaxialcompensated oil piston interrupting device is provided within a pressureconfining structure. Relatively movable contacts are arranged to operatewithin an arc extinguishing fluid in the structure and are separated todraw an arc to be extinguished by blast action within the structure. Aspring biased piston is axially arranged with the contacts and isprovided with a piston rod extending therethrough. One of the contactsand the piston rod engage each other in contact closed position. Meansare provided which are operative during circuit closing movement of thecircuit interrupter for engaging one of the contacts with the piston rodfor driving the piston to its biased position within the pressurestructure so that during a circuit opening operation the piston moves incontact opening direction for applying an impulse blast to the areimmediately after separation of the contacts.

It is, therefore, one object of this invention to provide a new andimproved circuit breaker structure for establishing and lengthening anarc.

Another object of this invention is to provide a new and improvedcircuit interrupting mechanism in which the relatively movable contactsand the fluid actuating piston are coaxially arranged.

A further object of this invention is to provide a new and improvedcircuit interrupting mechanism in which a fluid actuating pistonemploying two relatively movable States Patent parts is provided withmeans for equalizing the pressure on both sides thereof over at least apart of its working stroke.

A still further object of this invention is to provide a new andimproved circuit interrupting mechanism in which an oil impulse pistonemploys a closable opening forming a pressure equalizing passagetherethrough.

A still further object of this invention is to provide a new andimproved circuit interrupting mechanism in which an oil impulse pistonemploys a hollow, tubular piston rod forming a pressure equalizingpassage through the piston.

A still further object of this invention is to provide a new andimproved circuit interrupting device in which a hollow, tubular pistonrod forming a pressure equalizing passage through the piston engages themovable contact at its open end during contact closing operation anddisengages from the movable contact during its opening operation therebyexposing the equalizing passage to the arc gas pressure immediately uponcontact separation.

A still further object of this invention is to provide a new andimproved circuit interrupting mechanism in which a dual purpose inlet,outlet port is controlled by a valve means actuable to more than oneport controlling position determinable by the pressure created by theare.

A still further object of this invention is to provide a new andimproved circuit interrupting device employing a new fluid actuatingpiston utilizing two integrating parts.

Objects and advantages other than those set forth will be apparent fromthe following description when read in conjunction with the accompanyingdrawings, in which:

FIG. 1 is an elevational view partly in section of a circuit interrupterembodying the invention and shown in circuit closed position;

FIG. 2 is an enlarged sectional view through one of the interruptingdevices shown in FIG. 1 in the breaker closed position;

FIG. 3 is a cross sectional view taken along the line IIIlll of FIG. 2;

FIG. 4 is a cross sectional view taken along the line IVIV of FIG. 2;

FIG. 5 is a cross sectional view taken along the line V-V of FIG. 2;

FIG. 6 is an enlarged sectional view through one of the interruptingdevices shown in FIG. 1 during a contact disengaging operation;

FIG. 7 is an enlarged sectional view similar to FIG. 6 of the internalparts of the piston and relief valve shown in full pressure compensatingposition;

FIG. 8 is an enlarged view similar to FIGS. 6 and 7 of the internalparts of the piston and relief valve during excessive pressuredevelopment; and

FIG. 9 is an enlarged view of the structure shown in FIGS. 6, 7 and 8 inthe breaker open position.

Referring more particularly to the drawing by characters of reference,FIG. 1 illustrates an oil circuit breaker unit of the high voltage typesuch as that used in power transmission systems. Unit 11 is suspendedfrom one line terminal of the circuit interrupter in a suitable pressureconfining structure such as tank 12 and submerged in a suitableinsulating arc extinguishing fluid, such as oil. A conducting bridgingbar 13 serves to connect electrically the arc extinguishing unit 11 withan identical unit 14 in a manner well known in the art. Supported on acover 15 of the tank 12 are a pair of terminal bushings 16 and 17(partially shown), to the lower ends of which are secured arcextinguishing units 11 and 14. The cross bar 13 is actuated reciprocallyin the vertical direction by an insulating lift rod 18 to open and closerelatively movable cooperating contacts of the arc extinguishing units11 and 14.

FIG. 2 is an enlarged view in cross section of the left hand areextinguishing structure shown in FIG. 1. The right hand arcextinguishing structure is of similar design. In FIG. 2 the breaker isshown in its contact closed position and current passes from a conductor(not shown) in bushing 16 through a mounting plate 19 which is suitablyfastened to bushing 16 and is formed as an integral part of cylinder 20through plate 21, flange 22 of contact housing 23, collar 24, aplurality of contact elements such as finger contacts 25 into a movablerod shaped contact 26. Contact 26 is arranged in a pressure chamber 27which aids in extinguishing the are drawn between the relatively movablecontacts 25 and 26. Current flows in the contact closed position fromcontact 26 across the bridging bar 13 to the movable rod shaped contact26 arranged in unit 14 and through substantially identical parts in unit14 in reverse manner. The current loop through the cluster of relativelystationary finger contacts 25 and the contact housing 23 magneticallyincreases contact pressure of the finger contacts against the relativelymovable rod contact 26 at high magnitude currents in the well knownmanner.

The interrupting unit 11 comprises a metallic top section 28 and aninsulating lower section 29. The top section comprises a pump arrangedwithin cylinder 20 and employing a piston 30, nonmetallic piston rod 31extending from and through piston 30 and a driving spring 32. Piston 30and piston rod 31 are arranged for movement longitudinally of unit 11with the driving spring 32 being arranged between an inturned flangeforming valve seat 34 on one end of cylinder 20 and an outwardly turnedflange 35 on the periphery of the dome shaped piston 30. Two spacerrings 36 are arranged between spring 32 and flange 35 on the peripheryof piston 30. Cylinder 20 is clamped to the lower section 29 by aplurality of spaced bolts 37 one of which is shown in FIG. 2.

The piston rod 31 shown herein as a hollow push rod, extends throughcollar 24 and a clamping unit 39 and axially into contact housing 23. Aplurality of finger contacts 25 (note FIGS. 2 and are pivotally mountedin octagonally arranged grooves in collar 24 and rest with their arcingtips on the periphery of the movable rod shaped contact 26 within thecluster formed by these finger contacts. Contact pressure is provided bysprings 40 each seated with one end in a spring well 41 of fingercontacts 25 and in an insulating button 42 with the other end. Themovable contact 26 supports the piston rod 31 against the pressure orbias exerted by spring 32.

Piston 30 shown and described herein integrates with contact housing 23to form a piston means having two integrating parts i.e. a relativelymovable part such as piston 30 and a relatively stationary part such ascontact housing 23.

As shown more clearly in FIG. 3 the dome shaped piston 30 is providedWith a spider-like configuration freely venting fluid from one side tothe other side thereof through a plurality of apertures 43 therebyequalizing the pressure on both sides of the piston. A valve assembly 44loosely rests on the dome of piston 30 and is reciprocally guided by rod45 fastened to mounting plate 19 and arranged to extend longitudinallyof unit 11. The valve assembly 44 comprises a movable valve element 46biased against its valve seat 47 on the dome of piston 30 only by thecombined weight of compression spring 48 and valve element 46.Compression spring 48 rests in the valve assembly 44 and extends betweenit and mounting plate 19 substantially uncompressed when the circuitbreaker is in the closed position. As noted from FIG. 2 cylinder 20 hasa circular opening 50 in one end thereof formed by valve seat 34 inwhich valve element 46 is arranged. Between valve seat 34 and plate 19 aplurality of exhaust ports 51 are arranged which are controlled by valveelement 46. Cylinder 20 is provided with further openings or ports 52below spacer rings 36. Openings or ports 55 are provided in housing 23adjacent collar 24.

The clamping unit or nut 39 clamps the collar 24 and finger contacts 25to the contact housing 23. Housing 23 has a number of openings 53 (shownin FIGS. 2 and 4) through its bottom flange 54 arranged immediatelyunderneath spacer rings 36. Plate 21 is mounted to the bottom of flange56 of cylinder 20 by means of flathead screws 57. Flathead screws 58 tapinto flange 56 of cyl inder 20 to hold contact housing 23 to theunderside of plate 21. All three structural parts, namely cylinder 20,contact housing 23 and plate 21 are attached to the lower section 29 ofunit 11 by means of cap screws or bolts 37.

The lower section 29 of unit 11 comprises a plurality 'of spaced stackedbarrier plates 60 which are arranged within a shell 61. Shell 61 isprovided with two openings 62 which may be arranged (as shown) to extendthrough shell 61 in opposite directions. Built into the grid structureformed by the barrier plates 60 are the exhaust nozzles 63 whichprotrude through the openings 62. These nozzles are keyed in place bycheck tubes 65. A spacer 66 is interposed between the contact housing 23and a deflector 67 arranged at the inner end of the barrier plate stack.A gasket 68 made out of a resilient material such as a cork compositionis arranged between the barrier plate 69 and deflector 67 to provide atight stacking of the interrupting pot components of the lower section29. The barrier plates 69 and 70 form stufiing boxlike oil compartments.A metallic bottom plate 71 is fastened to the underside of shell 61 bymeans of a plurality of cap screws 72 (one of which is shown in FIG. 2).

For contact inspection cap screws 37 are removed and the whole shell 61with contents comes off. The tips of the finger contacts 25 then comeinto full view and can be readily examined. If the arcing tips ofcontacts 25 need dressing or if replacement is deemed necessary,flathead machine screws 58 are removed. With the removal of screws 58the contact housing 23 may be removed including the piston 30 and pistonor push rod 31. Piston 30 is able to pass through plate 21. Valveelement 46 and valve spring 48 also are removable with the contacthousing 23 so that the valve can be inspected. Spacers 36, however,cannot come out of cylinder 20 because plate 21 serves as a stop forthem. This is important because pump spring 32 biased against spacers 36is still highly compressed in the breaker open position.

Readjustment or realignment of the arcing contacts after contactinspection or replacement are not usually necessary because the contactscannot get out of alignment as they can only be mounted in the samecentral position. In applications where a plurality of interruptingunits similar to units 11 and 14 are used it might be desirable to havenozzles 63 face in a particular direction. This can be readilyaccomplished as the fastening screws 37 are displaced from each other 45degrees around the periphery of unit 11; thus one-eighth of a turn ormore of the lower section 29 can be readily obtained. The lowersections, however, are usually keyed in the desired position so that aselected position is always assured. In applications of this inventionutilizing a plurality of interrupting units 11 the metallic bottom plate71 becomes the lower terminus of voltage grading resistors (not shown)connecting the finger contact cluster and thi bottom plate. Bottom plate71 approaches the moving rod contact 26 close enough to establish aspark over circuit, thus placing the grading resistors in parallel withthe are on the inside of units 11 and 14.

The circuit breaker interrupting structure functions selectivelydepending upon the range of the magnitude of the current it has tointerrupt.

When interrupting low magnitude currents encountered at line droppingthe tripping impulse from a current transformer (not shown) causes anoperator of the circuit breaker (not shown) to move lift rod 18downwardly as shown in FIG. 1. Since the piston or push rod 31 rests onthe end of the movable contact 26, the whole piston assembly follows themovement of the movable contact 26 due to the pressure exerted by thespring 32. Piston 39 having a spider-like central portion passes oilreadily from the underside through apertures 43 to the space above thepiston thereby equalizing the pressure on both sides of the spider-likeportion of piston 30. The oil under the piston can readily escape out ofthe vent holes 52 in the side of cylinder 20 until these holes arecovered by the spacer rings 36 and the inner periphcry of piston 30engages with the outer periphery of the contact housing 23. At thispoint in its operation piston 30 becomes a pump and renders theequalizing effect of aperture 43 ineflective. At this moment thesimultaneous axial movement of the movable contact 26 and piston 39 andpiston rod 31 ceases. The movement of the piston slows down because ithas now become a pump and must displace the oil trapped under it in theannular space between cylinder 20 and contact housing 23. Up to thismoment the stored energy of the spring has been fed back into thecontact rod and added to its acceleration. Contact 26 now moves awayfrom the piston rod 31 and an arc is formed between the finger contacts25 and the tip of movable contact 26 at their separation. Gravity andsuction upon the downward movement of contact 26 have drawn valveassembly 44 out of its hole blocking position in flange or valve seat34. FIG. 2 illustrates valve assembly 44 in position wherein it isblocking the aperture or hole 50 formed by the inturned flange 34 ofcylinder 20. FIG. 6 illustrates the valve assembly drawn out of theaperture formed by flange 34. Fresh oil can freely flow through thishole from outside of unit 11 through passageways 51 to the space 77above piston 30. The top of piston 30 remains covered by the valveassembly 44 as the piston rod 31 moves downward with piston 30. The oilunder pressure of the pump formed by piston 30 and housing 23 now causesan impulse blast to flow into the void created by the retreating contact26 through the opening 53 in the bottom flange of the contact housing 23and attacks the arc concentrically. Some of the oil under pressure ofthe pump will bypass the contact 26 through the annular opening 78 indeflector 67. Thus, oil is in movement when the arc is drawn throughopening 78 in deflector 67. At an early current zero the insulating oilforced into the void by the pump will extinguish the arc and reestablishdielectric strength thus preventing reignition. The circuit is nowinterrupted.

When interrupting medium magnitude currents encountered at loadswitching and low power faults the initial phases of the interruptingoperation are the same as that described above for interrupting lowmagnitude currents up to the point of drawing an arc. As a power aredevelops, oil is decomposed and a gas pressure develops under thecluster formed by the finger contacts 25. This pressure is communicatedthrough the hollow pistonrod 31 to the space above piston 30. The oil inthe column formed in piston rod 31 is driven upward and the valveelement 46 is driven ofi of its valve seat as illustrated in FIG. 7into'the circular opening 50 thus blocking the exit passageways 51 Thepressure developed under the piston is thereby communicated throughpiston rod 31 to the now substantially sealed chamber above piston 30without loss of pressure and pressure compensation is achieved.Depending upon the magnitude of current and the developed pressures,spring 48 becomes compressed to a greater or lesser degree as the casemay be. However, the periphery of the valve element 46 keeps circularopening 50 substantially blocked throughout a predetermined range ofpressures. The pump is now able to squeeze oil into the arc zone becausethe pressures are equalized. The oil flow parallel to the arcintensifies as the arc lengthens through the hole 78 in deflector 67 andinto chambers 80 immediately behind nozzles 63. The developing pressuredrives the are into the openings of nozzles 63 where it is extinguishedat an early current zero.

When interrupting high magnitude currents which stem from heavy shortcircuits the interrupting operation follows the same pattern asdescribed above for interrupting medium magnitude currents encounteredat load switching and low power faults including the pressurecompensation of valve assembly 44. However, as the are energy increasesdue to the greater amount of electric power, the gas development becomesaccelerated and dangerous pressures are created. The increased pressureabove piston 30 compresses valve spring 48 driving valve element 46upward through the opening formed by flange 34 thereby openingpassageways 51 to the zone above piston 30 and relieving the pressuretherein as shown in FIG. 8. The balance of pressure below and abovepiston 30 is upset and compensation ceases. At the same time piston 30is driven upward by the extreme pressure developed underneath it. Thespacer rings 36 overrun the port holes 52 in cylinder 20 therebyrelieving the pressure in cylinder 20. The interrupting device nowfunctions as a pure suicidal device and interruption is achieved in theupper or lower nozzle chambers 80.

After the arc is interrupted and the circuit breaker is in its openposition the valve and piston assemblies assume the positions shown inFIG. 9. In each of FIGS. 6, 7 and 8 the paths of the pressure wavescreated by the arcs are illustrated by arrows.

To close the circuit breaker the movable contact 26 is moved upward byan operator (not shown) and the contact rod strikes the lower end of thepiston rod 31 some distance underneath the finger contacts 25 drivingthe piston assembly upward. As the valve assembly 44 is resting on topof the piston assembly, the hole formed by flange or valve seat 34 isopen. The oil above the piston assembly escapes free to the outside ofunit 11 through passageways 51 and dashpot action is prevented. As thespacer rings 36 clear ports 52 in cylinder 20* oil from outside of unit11 rushes in refilling the annular space around the contact housing 23.In contact closed position valve element 46 is now seated against valveseat 47 with its body closing the circular opening 50 in flange 34.Spring 32 is now compressed. In overtravel' piston 30 abuts theunderside of flange 34 after elevating the valve assembly 44 to aventing position similar to that shown in FIG. 8 to prevent dashpotreaction upon piston 30.

Although but a few embodiments of the present invention have beenillustrated and described it will be apparent to those skilled in theart that various changes and modifications may be made therein withoutdeparting from the spirit of the invention or from the scope of theappended claims.

Having now particularly described and ascertained the nature of my saidinvention and the manner in which it is to be performed, I declare thatwhat I claim is:

1. A circuit interrupter comprising a pressure confining structure,relatively movable contacts adapted to operate in said structure, an arcextinguishing fluid in said structure, means for separating saidcontacts to draw an arc to be extinguished by blast action within saidstructure, a cylinder arranged within said structure, a spring biasedpiston arranged within said cylinder and axially arranged with saidcontacts, a piston rod mounted to extend through said piston, one ofsaid contacts and said piston rod engaging each other in abuttingarrangement in contact closed position, means for equalizinng thepressure on both sides of said piston during a part of its stroke incontact opening direction, and means operative during circuit closingmovement of said interrupter for abutting said one of said contactsagainst said piston rod and driving said piston to its biased positionwithin said cylinder so that during a circuit opening operation saidpiston moves in contact opening direction for applying after apredetermined movement an impulse blast to the arc immediately afterseparation of said contacts.

2. A circuit interrupter comprising a pressure confining structure,relatively stationary and movable cooperating contacts adapted tooperate in said structure, said stationary contact comprising aclu'stei"of finger contact elements, an arc extinguishing fluid in saidstructure, means for separating said contacts to draw an arc to beextinguished by blastactio'n within said structure, a cyl inder arrangedwithin said structure, a spring biased piston arranged within saidcylinder and coaxially arranged with said contacts, a piston rod mountedto extend through said piston and into said cluster of finger contactelements, said movable contact and said piston rod engaging each otherin said cluster of finger contact elements in abutting arrangement incontact closed position, means for equalizing the pressure on both sidesof said piston during a part of its stroke in contact opening direction,and means operative during circuit closing movement of said interrupterfor abutting said one of said contacts against said piston rod anddriving said piston to its biased position Within said cylinder so thatduring a circuit opening operation said piston moves in contact openingdirection for applying after a predetermined movement an impulse blastto the arc immediately after separation of said contacts.

3. A circuit interrupter comprising a pressure confining structure,relatively movable contacts adapted to operate in said structure, an arcextinguishing fluid in said structure, means for separating saidcontacts to draw an arc to be extinguished by blast action within saidstructure, a cylinder arranged within said structure, a spring biasedpiston arranged within said cylinder and axially arranged with saidcontacts, a hollow piston rod mounted to extend through said piston forequalizing the pressure on both sides of said piston during a part ofits stroke, one of said contacts and said piston rod engaging each otherin abutting arrangement in contact closed position to close one end ofsaid piston rod, and means operative during circuit closing movement ofsaid interrupter for abutting said one of said movable contacts againstsaid piston rod and driving said piston to its biased position withinsaid cylinder, said piston rod and said one of said contacts movingtogether in abutting relationship during a part of said piston strokeand during the rest of said piston stroke separating from said one ofsaid contacts for applying an impulse blast to the are immediately afterseparation of said contacts.

4. A circuit interrupter comprising a pressure confining structure,relatively movable cooperating contacts adapted to operate in saidstructure, an arc extinguishing fluid in said structure, means forseparating said contacts to draw an arc to be extinguished by blastaction within said structure, a spring biased piston means arrangedwithin said structure, said piston means comprising two integratingparts, one of said parts being movable relative to the other part duringa part of the movement of said piston means, said movable part beingprovided with means for equalizing the pressure on both sides thereofduring at least a part of its movement relative to said other part, oneof said contacts and at least one of said parts of said piston meansengaging each other in abutting arrangement in contact closed position,and means operative during circuit closing movement of said interrupterfor abutting said one of said movable contacts against said one of saidparts of said piston means and driving said piston means to its biasedposition Within said structure, said piston means and said one of saidcontacts moving together in abutting relationship during a part of thepiston stroke in contact opening direction and during the rest of thepiston stroke separating from said one of said contacts for applying animpulse blast to the are immediately after separation of said contacts.

5. A circuit interrupter comprising a pressure confining structure,relatively movable cooperating contacts adapted to operate in saidstructure, an arc extinguishing fluid in said structure, means forseparating said contacts todraw an arc to beextinguished by blast actionwithin saidstr'uc'ture, a spring biased piston means arranged withinsaid structure, said piston means comprising two integrating parts, oneof said parts being movable relative to the other part during a part ofthe movement of said piston means, said movable part being provided withmeans for equalizing the pressure on both sides thereof during at leasta part of its movement relative to said other part, a piston rod mountedon said one of said parts to extend through said piston means, one ofsaid contacts and said piston rod engaging each other in abuttingarrangement in contact closed position, and means operative duringcircuit closing movement of said interrupter for abutting said one ofsaid movable contacts against said piston rod and driving said pistonmeans to its biased position within said structure, said piston rod andsaid one of said contacts moving together in abutting relationshipduring a part of the piston stroke in contact opening direction andduring the rest of the piston stroke separating from said one of saidcontacts for applying an impulse blast to the are immediately afterseparation of said contacts.

6. A circuit interrupter comprising a pressure confining structure,relatively movable contacts adapted to operate in said structure, an arcextinguishing fluid in said structure, means for separating saidcontacts to draw an arc to be extinguished by blast action within saidstructure, a spring biased piston means arranged Within said structureand axially arranged with said contacts, said piston means comprisingtwo integrating parts, one of said parts being movable relative to theother part, said movable part being provided with means for equalizingthe pressure on both sides thereof during a part of its movementrelative to said other part, a piston rod mounted on said one of saidparts to extend through said piston means, one of said contacts and saidpiston rod engaging each other in abutting arrangement in contact closedposition, and means operative during circuit closing movement of saidinterrupter for abutting said one of said movable contacts against saidpiston rod and driving said piston means to its biased position withinsaid structure, said piston rod and said one of said contacts movingtogether in abutting relationship during a part of the piston stroke incontact opening direction and during the rest of the piston strokeseparating from said one of said contacts and engaging said other partfor applying an impulse blast to the are immediately after separation ofsaid contacts.

7. A circuit interrupter comprising a pressure confining structure,relatively movable contacts adapted to operate in said structure, an arcextinguishing fluid in said structure, means for separating saidcontacts to draw an arc to be extinguished by blast action within saidstructure, a cylinder arranged Within said structure, a spring biasedpiston means arranged within said cylinder and axially arranged withsaid contacts, said piston means comprising two integrating parts, oneof said parts being movable relative to the other part, said movablepart being provided with means for equalizing the pressure on both sidesthereof during a first part of its movement relative to said other part,a hollow piston rod mounted on said one of said parts to extend throughsaid piston means, said hollow piston rod forming a passage therethroughfor equalizing the pressure on both sides of said piston means underpredetermined conditions during a second part of the movement of saidone of said parts, one of said contacts and said piston rod engagingeach other in abutting arrangement in contact closed position to closeone end of said piston rod, and means operative during circuit closingmovement of said interrupter for abutting said one of said movablecontacts against said piston rod and driving said piston means to itsbiased position within said cylinder, said piston rod and said one ofsaid contacts moving together in abutting relationship during a part ofthe piston stroke in contact opening direction and during the rest ofthe piston stroke separating from said one of said contacts and engagingsaid other part for applying an impulse blast to the arc immeditaelyafter separation of said contacts.

8. A circuit interrupter comprising a pressure confining structure,relatively movable contacts adapted to operate in said structure, an arcextinguishing fluid in said structure, means for separating saidcontacts to draw an arc to be extinguished by blast action within saidstructure, a cylinder arranged within said structure, a spring biasedpiston means arranged within saidcylinder and substantially axiallyarranged with said contacts, said piston means comprising twointegrating parts, one of said parts being movable relative to the otherpart, said movable part being provided with means for equalizing thepressure on both sides thereof during a first portion of its movementrelative to said other part, said equalizing means being renderedinefiective by said other part during a second portion of the movementof said movable part, a hollow piston rod mounted on said one of saidparts to extend through said piston means, one of said contacts and saidpiston rod engaging each other in abutting arrangement in contact closedposition to close one end of said piston rod, and means operative duringcircuit closing movement of said interrupter for abutting said one ofsaid movable contacts against said piston rod and driving said pistonmeans to its biased position within said cylinder, said piston rod andsaid one of said contacts moving together in abutting relationshipduring a part of the piston stroke and during the rest of the pistonstroke separating from said one of said contacts for applying an impulseblast to the arc immediately after separation of said contacts;

9. A circuit interrupter comprising a pressure confining structure, apair of cooperating contacts, one of said contacts being relativelymovable and the other of said contacts being relatively stationary, saidcontacts being adapted to operate in said structure, said stationarycontact comprising a cluster of finger contact elements, an arcextinguishing fluid in said structure, means for separating saidcontacts to draw an arc to be extinguished by blast action within saidstructure, a cylinder arranged within said structure, a spring biasedpiston means arranged within said cylinder and coaxially arranged withsaid contacts, said piston means comprising two integrating parts, oneof said parts being movable relative to the other part, said movablepart being provided with means for equalizing the pressure on both sidesthereof during a first portion of its movement relative to said otherpart, said equalizing means being rendered ineffective by said otherpart during a second portion of the movement of said movable part, ahollow piston rod mounted on said one of said parts to extend throughsaid piston into said cluster of finger contact elements, one of saidcontacts and said piston rod engaging each other in abutting arrangementin said cluster of finger contact elements in contact closed position toclose one end of said piston rod, and means operative during circuitclosing movement of said interrupter for abutting said one of saidmovable contacts against said piston rod and driving said piston meansto its biased position within said cylinder, said piston rod and saidone of said contacts moving together in abutting relationship during apart of said piston stroke and during the rest of said piston strokeseparating from said one of said contatcs for applying an impulse blastto the arc immediately after separation of said contacts.

10. A circuit interrupter comprising a pressure confining structure,relatively movable contacts adapted to operate in said structure, an arcextinguishing fiuid in said structure, means for separating saidcontacts to draw an arc to be extinguished by blast action within saidstructure, a cylinder arranged within said structure, port holesarranged within said cylinder, a spring biased piston means arrangedwithin said cylinder and axially arranged with said contacts, saidpiston means comprising two integrating parts, one of said parts beingmovable relative to the other part, said movable part being providedwith means for equalizing the pressure on both sides thereof during atleast a part of its movement relative to said other part, said movablepart blocking said port holes during a part of its movement relative tosaid other part to provide a pumping action, one of said contacts andsaid piston engaging each other in abutting arrangement in contactclosed position, and means operative during circuit closing movement ofsaid interrupter for abutting said one of said movable contact againstsaid piston means and driving said piston means to its biased positionwithin said cylinder, said piston means and said one of said contactsmoving together in abutting relationship during a part of the pistonstroke in contact opening di rection and during the rest of the pistonstroke separating from said one of said contacts for applying an impulseblast to the arc immediately after separation of said contacts.

11. A circuit interrupter comprising a pressure confining structure,relatively movable contacts adapted to operate in said structure, an arcextinguishing fluid in said structure, means for separating saidcontacts to draw an arc to be extinguished by blast action within saidstructure, a port arranged in and at one end of said structure, acylinder arranged in said structure, one end of said cylinder at saidone end of said structure defining a valve seat, a valve elementarranged within said structure for cooperating with said seat to controlsaid port, a spring biased piston movably arranged within said cylinder,said piston defining an opening extending therethrough, one of saidcontacts being arranged to engage with said piston to close saidopening, and means operative during circuit closing movement of saidinterrupter for abutting said one of said contacts against said pistonat the other end of said cylinder to close said opening and to drivesaid piston to its biased position within said cylinder so that during acircuit opening operation said piston moves in contact opening directionfor applying after a predetermined movement an impulse blast to the areimmediately after, separation of said contacts and uncovering of saidopening, said valve element cooperating with said valve seat to closesaid port upon drawing of an arc until the pressure created by the arcexceeds a predetermined value.

12. A circuit interrupter comprising a pressure confining structure,relatively movable contacts adapted to operate in said structure, an arcextinguishing fluid in said structure, means for separating saidcontacts to draw an arc to be extinguished by blast action within saidstructure, a port arranged in and at one end of said structure, acylinder arranged in said structure, one end of said cylinder at saidone end of said structure defining a valve seat, a spring biased valveelement arranged within said structure for cooperating with said seat tocontrol said port, a spring biased piston movably arranged within saidcylinder, said piston defining an opening extending therethrough, one ofsaid contacts being arranged to engage with said piston to close saidopening, and means operative during circuit closing movement of saidinterrupter for abutting said one of said contacts against said pistonat the other end of said cylinder to close said opening and to drivesaid piston to its biased position within said cylinder so that during acircuit opening operation said piston moves in contact opening directionfor applying after a predetermined movement an impulse blast to the arcimmediately after separation of said contacts and uncovering of saidopening, said valve element under pressure created by the arc beingactuated to cooperate with said valve seat to close said port until thepressure created by the arc exceeds a predetermined value.

13. A circuit interrupter comprising a pressure confining structure,relatively movable contacts adapted to operate in said structure, an arcextinguishing fluid in said structure, means for separating saidcontacts to draw an arc to be extinguished by blast action within saidstructure, a port arranged in and at one end of said structure, acylinder arranged in said structure, one end of said cylinder at saidone end of said structure defining a valve seat, a spring biased valveelement arranged within said structure for cooperating with said seat tocontrol said port, a spring biased piston movably arranged Within saidcylinder, a piston rod defining an opening extending through saidpiston, one of said contacts being arranged to engage with said pistonrod to close said opening, and means operative during circuit closingmovement of said interrupter for abutting said one of said contactsagainst said piston rod at the other end of said cylinder to close saidopening and to drive said piston to its biased position within saidcylinder so that during a circuit opening operation said piston moves incontact opening direction for applying after a predetermined movement animpulse blast to the arc immediately after separation of said contactsand uncovering of said opening, said valve element under pressurecreated by the are being actuated to cooperate with said valve seat toclose said port until the pressure created by the arc exceeds apredetermined value.

14. A circuit interrupter comprising a pressure con-' fining structure,relatively movable contacts adapted to operate in said structure, an arcextinguishing fluid in said structure, means for sepaarting saidcontacts to draw an arc to be extinguished by blast action within saidstructure, a port arranged in and at one end of said structure, acylinder arranged in said structure, one end of said cylinder defining avalve seat, a valve element arranged within said structure forcooperating with said seat to control said port, a spring biased pistonmovable arranged within said cylinder, a piston rod defining an openingextending through said piston, one of said contacts being arranged toengage With said piston rod to close said opening, and means operativeduring circuit closing movement of said interrupter for abutting saidone of said contacts against said piston rod at the other end of saidcylinder to close said opening and to drive said piston to its biasedposition Within said cylinder so that during a circuit opening operationsaid piston moves in contact opening direction for applying after apredetermined movement an impulse blast to the are immediately afterseparation of said contacts and uncovering of said opening, said valveelement under a first predetermined range of pressures created by theare being driven against its spring bias to cooperate with said valveseat to close said port, said valve element when the pressures createdby the arc exceeds said predetermined range being driven against itsspring bias to a position Where said valve element opens said port.

15. A circuit interrupter comprising a pressure confining structurecontaining an arc extinguishing fluid wherein a pair of relativelymovable cooperating contacts are adapted to operate in said structure, aresiliently biased piston arranged axially With at least one of saidcontacts and equalizing the pressure on both sides thereof during a partof its stroke and acting as a pump during another part of its stroke,said one of said contacts engaging said piston in contact closedposition to drive said piston to its biased position so that during acircuit opening operation said piston moves in contact opening directionand after a predetermined movement thereof applying an impulse blast tothe arc immediately after separation of said contacts.

References Cited in the file of this patent UNITED STATES PATENTS2,462,724 Cumming Feb. 22, 1949 2,525,494 Ludwig et al. Oct. 10, 1950FOREIGN PATENTS 796,191 France Jan. 17, 1936 705,359 Germany Apr. 25,1941

